ACB sources said Kumar will have to meet the case investigating officer on Wednesday.

The investigating agency has registered an FIR in the alleged irregularities related to the water tankers in 2012 during the previous Congress government. The tanker scam hit headlines last week after sacked water minister Kapil Mishra filed a complaint against Kejriwal accusing him of shielding water mafia and scuttling the report of the fact-finding committee in the scam.

ACB sources said that Kumar is the first of the many other Delhi government officials who would be probed in the case. Mishra, who is on a hunger strike, will visit the ACB headquarters on Monday to record his statement for the second time. Mishra, who was the water minister until May 7, has threatened to expose the CM’s alleged role in the case. The former water minister has also claimed that he had offered to be an ACB witness in the case.

In August 2016, ACB officials questioned former chief minister Sheila Dikshit’s alleged role in the case. Speaking to a news agency, the former Delhi CM denied any wrongdoing and said Mishra’s going to ACB was an internal dispute of the Aam Aadmi Party.

ACB sources said they are taking Mishra’s detailed statement and would call CM Kejriwal for questioning at a later stage. On May 8, Mishra had posed for photographers during his visit to the ACB headquarters. Mishra had showed a sealed envelope he reportedly later submitted to the ACB. “Confidential. Role of Arvind Kejriwal and his close associates in tanker scam,” read the envelope.